execsnoop: enable tracing_on for good measure

[aktau]

I was lately trying to run execsnoop on my workstation and seeing nothing being printed out. Confused, I read the script and tried catting all sorts of values in /sys/kernel/debug/tracing. To my surprise, tracing_on contained 0. Doing echo 1 > tracing_on thus fixed the problem.

I see that execsnoop doesn't deal with tracing_on, so maybe it would be good to just put a echo 1 > tracing_on in there?

I find it strange that I only encounter this now, as a cursory Google search tells me that tracing_on has been present in Linux kernels since forever.

[scotte]

Same as #41?

[brendangregg]

Any idea why tracing_on is 0? Ever used trace-cmd or KernelShark or something?

On all my systems it is 1 by default. I'd like to know why it is 0 before forcing it to 1, in case I'm breaking something (like another tracer that is using it.)

[EvanTheB]

It is set to 0 at boot on my chromebook, but I dont know why. Maybe a check+warn instead of a set?